I've found also an operating description to replace it:Heaps of Philips based CD players have this problem, but the only one of mine that I've had to replace the gear on was coincidentally a Marantz CD 52 mkII.

- Take the top cover off (four side screws, two at back)
- Remove the disc clamp by swinging it vertical, where it will lift out
- Slide the disc tray out a couple of inches
- Remove the disc tray faceplate by pushing on the top of the faceplate while pulling at the bottom lip of it
- Remove the front panel of the player by undoing the three screws along the top of it and unsnaping the clips on either end. It will hinge away from the base of the player
- Pull the disc tray all the way out
- Slip the belt of the tray gear, and lever apart the two plastic supports to remove the gear
- Put the new gear in, and reassemble the player in reverse order to that above

A couple of hints on reassembly:
- To put the faceplate back on, press in on off centre to the left by half an inch or so, then slip it to the right. It should latch.
- The leftward disc tray guides are spring loaded, and need to be depressed somewhat to put the disc tray back in.

Have you got a replacement gear yet? I've got one for you if you don't.

Good luck,
Anton

Thanks to Anton

Good luck to you.

I modified my DD52mkII with a very pleasant result (replacing originals AOPs with LM4562, suppressing the 4 muting transistors, and replacing the 2 electrolytics link capacitors of analogic output by 4.7µF MKT).
Listening is very, but very better on all band.
Very Neutral and clear, also on forte.
The bass are a little less loud than before, but tight.
Voices and medium reveales the legendary quality of the
nad 3020i and the LS3/3a (DIY).
The high frequency go long and very pure.